Nanoparticles are particles having nanoscale particle sizes, and show optical, electrical and magnetic properties completely different from those of bulk materials due to a large specific surface area and the quantum confinement effect, in which energy required for electron transfer changes depending on the size of material. Accordingly, due to such properties, much interest has been concentrated on their applicability in the catalytic, electromagnetic, optical, medical fields, and the like. Nanoparticles may be considered as intermediates between bulks and molecules, and may be synthesized in terms of two approaches, that is, the “top-down” approach and the “bottom-up” approach.
Examples of a method for synthesizing a metal nanoparticle include a method for reducing metal ions in a solution by using a reducing agent, a method for synthesizing a metal nanoparticle using gamma-rays, an electrochemical method, and the like, but in the existing methods, it is difficult to synthesize nanoparticles having a uniform size and shape, or it is difficult to economically mass-produce high-quality nanoparticles for various reasons such as problems of environmental contamination, high costs, and the like by using organic solvents.
Meanwhile, in order to prepare metal nanoparticles in the related art, metal nanoparticles have been prepared by synthesizing particles with a low reduction potential, such as Ag, Cu, Co, and Ni, substituting the surface of particles, such as Ag, Cu, Co, and Ni with a metal having a higher reduction potential than the particles, for example, Pt, Pd, or Au by a potential difference substitution method, and after the surface substitution, melting Ag, Cu, Co, Ni, and the like remaining inside the particles through an acid treatment. In this case, there is a problem in the process in that a post-treatment needs to be performed with an acid, and since the potential difference substitution method is a natural reaction, there are few factors that may control the post-treatment, and thus it is difficult to prepare uniform particles. Therefore, there is a need for a method for easily preparing uniform metal nanoparticles.